As is well known, vehicles, and in particular large trucks, are provided with scissors-type suspensions capable of cushioning extremely heavy loads unlike those normally encountered in the smoother ride of a passenger car. In order to isolate the driver from fatigue and discomfort induced by the vehicle vibrations, it is normal practice to provide seat suspension systems incorporating various spring arrangements which protect the driver from vibrations at the expense of consuming a considerable amount of physical space beneath the seat. This is especially applicable to spring suspension systems which can be adjusted according to the weight of the seat occupant. Some of these seats include slide provisions which enable a fore and aft or longitudinal adjustment of the seat relative to the floor of the vehicle. When a seat is provided with both of the aforementioned adjustments, it must locate its seat frame a considerable distance above the vehicle floor to accommodate them. In addition, the partial collapsibility of the scissors linkage used in these suspensions also contributes to the distance at which the seat is mounted. Often, this distance becomes prohibitively high to be utilized in certain vehicles having relatively small space limitations between the floor and the ceiling. Accordingly, it remains desirable to provide a seat suspension incorporating both a seat occupant weight compensation adjustment and a fore and aft seat adjustment which together with a substantially fully collapsible scissors linkage will ensure a relatively low profile for the seat.
It is a principal object of the invention to provide a suspension mechanism that is simply constructed and relatively inexpensive while still meeting manufacturers' ever increasing demands for compactness and comfort.
It is also an object of the invention to provide a suitable suspension unit which will reduce the shocks and vibration transmitted from the vehicle to a driver via the driver's seat.
It is a further object of the invention to provide a seat suspension having an adjustable preload to suit the weight of the seat occupant.
It is another object of the invention to provide a seat suspension utilizing a scissors linkage having slide channels which serve as guides for the longitudinal adjustment of the seat.
It is another object of the invention to provide a seat suspension having a substantially full collapsible scissors linkage.
It is yet another object of the invention to provide a seat suspension employing different types of springs.
Still another object of the invention is to provide a more comfortable ride throughout the operational range of the seat suspension.
The present invention advantageously provides a vehicle seat suspension employing a force storage compression spring assembly whose initial force is adjustable by selectively shifting the height of a camming mechanism. The seat suspension also relies on a fore and aft adjustment strategically confined in the existing frame supporting the seat.
In one aspect of the invention, a low profile vehicle seat suspension comprises a bottom frame adapted to be mounted on the vehicle and a top frame located above the bottom frame and adapted to support a seat thereon. A scissors linkage is interconnected between the bottom frame and the top frame and enables the bottom frame and the top frame to move relative to each other substantially in parallelism. A biasing arrangement is disposed between the top frame and the bottom frame and has a preload force urging the top frame away from the bottom frame. A first adjustment mechanism is located in the top frame and selectively enables fore and aft adjustment of the top frame relative to the bottom frame. A second adjustment mechanism is located between the bottom frame and the top frame and selectively enables an adjustment on the biasing arrangement in accordance with the weight of an occupant in the seat by translating a horizontal force applied along the bottom frame into a vertical force affecting the preload force of the biasing arrangement.
In another aspect of the invention, an adjustable vehicle seat comprises a bottom frame adapted to be mounted on the vehicle, and a top frame located above the bottom frame and adapted to support a seat thereon. A scissors linkage having a spring support interconnects the bottom frame and the top frame and constrains the top frame to vertical movement relative to the bottom frame. A spindle extends upwardly from the bottom frame and an adjustment plate is slidably disposed on the bottom frame, the adjustment plate having a opening formed by a continuous wall through which the spindle projects in spaced relationship to the wall. A cam is fixed to the adjustment plate and encircles the spindle in spaced relationship therewith. A cam follower having an outwardly extending lip is movably mounted upon the cam and encircles the spindle. A spring has one end seated against the spring support and another end seated against the lip. The spring has a preload force applied thereto urging the top frame away from the bottom frame. Sliding the adjustment plate and the cam towards the spindle causes the cam follower to move upwardly to further compress and add to the preload force on the spring.
In yet another aspect of the invention, a vehicle seat suspension comprises a bottom frame adapted to be mounted on the vehicle, the bottom frame having a pair of spaced front channels secured thereto and a pair of spaced bottom rear channels secured thereto and located rearwardly of the bottom front channels. A top frame is located above the bottom frame and is adapted to supported a seat thereon. Top frame has a pair of spaced top front channels depending therefrom and a pair of spaced adjustment channel assemblies depending therefrom and located rearwardly of the top front channels. Each of the adjustment channel assemblies comprise an adjusting channel formed with a plurality of slots therethrough, a front ear secured to a forward end of the adjusting channel, a rear ear joined to a rear end of the adjusting channel, each of the ears being formed with an opening therethrough, a comb having a multiplicity of teeth, a front tab secured to a forward end of the comb and a rear tab secured to a rear end of the comb, each of the tabs being formed with an aperture therethrough. Each adjusting channel is juxtaposed relative to the comb such that the teeth of the comb are receivable in the slots of the adjusting channel and the openings in the ears are aligned with the apertures in the tabs. Each of the adjustment channel assemblies also comprise a rotatable release rod extending through the aligned openings and the apertures and fixed to the comb, and a torsion spring interposed between the front ear of the adjusting channel and the front tab of the comb and encircling a portion of the release rod so as to normally urge the teeth into engagement with the slots. A connecting wire joins each of the adjustment channel assemblies and transmits rotation of one of the release rods to the other of the release rods. A substantially fully collapsible scissors linkage is interconnected between the top frame and the bottom frame. A biasing arrangement is disposed between the top frame and the bottom frame for urging the top frame away from the bottom frame. The scissors linkage includes a pair of outer links and a pair of inner links, a mid portion of each of the outer links being pivotally connected to a mid portion of the inner links. Each of the outer links and each of the inner links has front ends and rear ends, the front ends of the inner links being connected by a transverse shaft, each end of which carries a first slide block slidably receivable in one of the top front channels on the top frame. The rear ends of the rear links are joined together by a cross shaft, each of which carries a stationary block receivable in one of the bottom rear channels on the bottom frame. The front ends of the outer links each carry a second slide block slidably receivable in one of the bottom front channels on the bottom frame. The rear ends of the outer links are connected by a cross member, each end of which carries an adjusting block slidably receivable in one of the adjustment channel assemblies on the top frame. Each of the adjusting blocks has a bottom surface formed with grooves matable with the teeth on the comb. Selective rotation of the release rod against the bias of the torsion spring moves the teeth on the combs out of engagement with the slots on the adjusting channels and out of engagement with the grooves on the adjusting blocks allowing the latter to slide in the adjusting channels to provide a fore and aft adjustment of the seat on the top frame relative to the bottom frame. The release of the release rod returns the teeth to the slots and the grooves of the adjusting blocks thereby locking the seat in position.
Various other objects, features and advantages of the invention will be made apparent from the following description taken together with the drawings.